Which of the following are true regarding large-volume jet nebulizers?

a. A variable air-entrainment port allows air mixing and different FiO2 values.
b. Liquid particles are generated by mechanical vibration energy.
c. They are pneumatically powered and attach directly to a flowmeter.
d. Baffling causes impaction or removal of large, unstable particles.
a. 1 and 3 only
b. 1, 2, and 3 only
c. 2 and 4 only
d. 1, 3, and 4 only

ANS: D
As depicted in Figure 38-13, these devices are pneumatically powered, attaching directly to a flowmeter and compressed gas source. Liquid particle aerosols are generated by passing gas at a high velocity through a small "jet" orifice. The resulting low pressure at the jet draws fluid from the reservoir up to the top of a siphon tube, where it is sheared off and shattered into liquid par-ticles. The large, unstable particles fall out of suspension or impact on the internal surfaces of the device, including the fluid surface (baffling). The remaining small particles leave the nebulizer through the outlet port, carried in the gas stream. A variable air-entrainment port allows air mix-ing to increase flow rates and to alter FiO2 levels.